@misc{10481/59535,
year = {2019},
url = {http://hdl.handle.net/10481/59535},
abstract = {Chemotaxis and energy taxis permit directed bacterial movements in
gradients of environmental cues. Nitrate is a final electron acceptor for anaerobic
respiration and can also serve as a nitrogen source for aerobic growth. Previous
studies indicated that bacterial nitrate taxis is mediated by energy taxis mechanisms,
which are based on the cytosolic detection of consequences of nitrate metabolism.
Here we show that Pseudomonas aeruginosa PAO1 mediates nitrate chemotaxis on
the basis of specific nitrate sensing by the periplasmic PilJ domain of the PA2788/
McpN chemoreceptor. The presence of nitrate reduced mcpN transcript levels, and
McpN-mediated taxis occurred only under nitrate starvation conditions. In contrast
to the NarX and NarQ sensor kinases, McpN bound nitrate specifically and showed
no affinity for other ligands such as nitrite. We report the three-dimensional structure
of the McpN ligand binding domain (LBD) at 1.3-Å resolution in complex with
nitrate. Although structurally similar to 4-helix bundle domains, the ligand binding
mode differs since a single nitrate molecule is bound to a site on the dimer symmetry
axis. As for 4-helix bundle domains, ligand binding stabilized the McpN-LBD
dimer. McpN homologues showed a wide phylogenetic distribution, indicating that
nitrate chemotaxis is a widespread phenotype. These homologues were particularly
abundant in bacteria that couple sulfide/sulfur oxidation with nitrate reduction. This
work expands the range of known chemotaxis effectors and forms the basis for the
exploration of nitrate chemotaxis in other bacteria and for the study of its physiological
role.},
organization = {This work was supported by FEDER funds and Fondo Social Europeo through grants
from the Junta de Andalucía (grant CVI-7335) and the Spanish Ministry for Economy
and Competitiveness (grants BIO2013-42297, BIO2016-76779-P, and BIO2016-74875-P).
We furthermore acknowledge NIH grant P30 DK089507, which financed the generation
of bacterial mutants},
publisher = {American Society for Microbiology},
keywords = {Pseudomonas aeruginosa},
keywords = {Chemoreceptor},
keywords = {Chemotaxis},
keywords = {Nitrates},
title = {The Molecular Mechanism of Nitrate Chemotaxis via Direct Ligand Binding to the PilJ Domain of McpN},
doi = {10.1128/mBio.02334-18},
author = {Martín Mora, David and Ortega, Álvaro and Matilla, Miguel and Martínez Rodríguez, Sergio and Gavira Gallardo, José Antonio and Krell, Tino},
}